Generating quiz questions and monitoring quiz
function is a lot of work on top of regular
teaching. Because I was letting students repeat the
quiz up to three times each week (top score counted), each
10-question quiz was a random draw from a larger pool of
questions. The
day a student showed up for an exam with quiz questions
and answers printed out onto flash cards, I knew I
needed to push them beyond memorization! I found
that I needed at least 15 questions in the pool for each
quiz, and more was better.

With this much work, the question in my mind was whether
it made any difference to student outcomes. Did it just
give the most-prepared students another way to earn
credit, or did it actually help them move beyond
memorization of factual material and into procedural
thinking - on the path towards independence in learning?
(I take these stages from cognitive developmental theory
in Women's Ways of Knowing, Belenky, Clincy,
Goldberger & Tarule 1986.)

To answer this question, I analyzed student performance as
a function of two variables: initial knowledge (measured
as performance on the first in-class summative exam) and
number of weeks that the student took at least one quiz. I
didn't consider score on the quiz or how often the quiz
was taken. Performance was calculated as the sum
scores of the other three in-class exams (as mentioned elsewhere,
the exams and quizzes had questions with similar
structure, distributed similarly in Bloom's taxonomy).

I am preparing these results for publication, and here
only provide a graphical representation of my findings. I
calculated the residuals of the regression of (sum scores
exams 2, 3, and 4) against first exam score as a measure
of student improvement. Graphing these resituals against
number of quizzes taken (13 is the maximum) clearly shows
that nearly all students benefited from taking weekly
quizzes. (Other analyses show that better, or worse,
performing students are not more or less likely to take
the quizzes).

Interestingly,
there are students who fail to improve no matter how many
quizzes they take (lower right quadrant) and who fail to
take quizzes despite poor performance (lower left
quadrant). These students are the focus of on-going
research, as they appear to demonstrate what is sometimes
termed the "feedback gap:" failure to reflect on
performance and alter study habits in response to
feedback.